The present invention relates to a plug, also known as a xe2x80x9ccollarxe2x80x9d or an xe2x80x9canchorxe2x80x9d, such as the ones used for operatively connecting torsion springs to overhead shafts of counterbalancing mechanisms used for garage doors and the like, in order to allow a torque transfer between the torsion spring and the overhead shaft so as to counterbalance such cable-operated doors.
It is known in the art that large, vertical, cable-operated doors, such as commercial and residential sectional garage doors, usually require counterbalancing mechanisms to counterbalance the weight of the door in order to decrease the force required to open the door and also facilitate its closing from a raised to a lowered position. Large sectional garage doors used in commercial and residential applications may be manually or power operated. In either case, but particularly for manually operated doors, counterbalancing mechanisms have been used for many years to counterbalance the weight of the door and control its opening and closing movements so that one person can easily control the operation of the door. Counterbalancing mechanisms are also advantageous for power operated overhead doors since they reduce the power requirements needed for the motor and they lower the structural strength required for the door opening and closing mechanism. In other words, lighter weight, lower cost, door controlling mechanisms may be used if a counterbalancing mechanism is connected to the door to assist it in its opening and closing movements. Furthermore, the provision of a counterbalancing mechanism minimizes the chance of a rapid and uncontrolled closing of the door in the event of a failure of the door opening and closing mechanism, which can result in serious injury or damage.
It is also known in the art that a widely used type of counterbalancing mechanism generally comprises a pair of spaced apart cable drums connected to flexible cables, each cable being in turn connected to a lower opposite side edge of the garage door. The cable drums are usually mounted on a overhead shaft which is supported above the door opening and is connected to one or more torsion springs which are each fixed to the shaft at one end, and secured to a fixed structure such as the wall for example at the other end, so that the cable drums are biased to rotate in a direction which winds the cables onto the drums and counteracts the weight of the door connected to the cables. The torsion springs are adjusted to properly balance the weight of the door so that minimal opening and closing efforts are required, either manually or when motor controlled.
It is also known in the art that conventional, low cost adjustment devices used for the above-mentioned type of counterbalance mechanism, and widely utilized in the garage door industry, are generally cylindrical xe2x80x9ccollarsxe2x80x9d commonly referred to also as xe2x80x9cplugsxe2x80x9d (or xe2x80x9cconesxe2x80x9d) which are connected to the so-called fixed ends of the torsion springs and are thus mounted on the aforementioned shaft for adjusting the deflection of the springs to preset the counterbalance force. The aforementioned collars usually include one or more setscrews which lock the collars to the shaft to prevent rotation thereabout except during normal adjustment of the spring deflection. The collars also usually include sockets for receiving winding bars whereby the springs are manually preset, or xe2x80x9cpreloadedxe2x80x9d, by rotating the collars with respect to the shaft using the winding bars and then locking the collars to the shaft with the setscrews. Each collar also may include a slot onto which a corresponding free end of the torsion spring is hooked on. These slots are usually T-shaped, and are thus commonly known as xe2x80x9cT-slotsxe2x80x9d.
An important problem associated with the aforementioned type of counterbalancing mechanism, or with any other type of counterbalancing mechanism which uses winding collars (also known as xe2x80x9canchorsxe2x80x9d) having T-slots and tensioning springs, arises when the radial space between the inside of the collar and the outside of the shaft is limited. Given the fact that most overhead shafts employed in the industry are usually of standard diameter, the above-mentioned problem generally arises either when the shaft is covered with an additional fitting placed thereabout, or when the torsion spring mounted about the shaft (which may or may not be covered with an additional fitting) has a reduced inside diameter. In the first case, when the radial space between the shaft and the torsion spring is limited as a result of a shaft being covered with an additional fitting so as to protect the shaft and/or transfer the load, collars having larger inside diameters are required to be able to mount them onto the fitting-covered shaft. Not only are large inside diameter collars more expensive, but they need to be used with torsion springs having larger inside diameters in order to render the counterbalancing mechanism operable. Torsion springs having large inside diameters (i.e. greater than 2xe2x80x3) are also more expensive and are limited in choice, that is, they are not readily available because most of the torsion springs being used in the industry have generally an inside diameter of equal to or less than 2xe2x80x3. Now, in the second case, that is, when the radial space between the shaft and the torsion spring is limited as a result of using torsion springs having reduced inside diameters, the free ends of such springs hooked onto the plugs do not allow the latter to be mounted about the overhead shafts. There is simply not enough clearance between the shaft and the collar for a spring""s free end (also known as a xe2x80x9cspring tailxe2x80x9d) to be lodged thereinbetween, and as a result, the collars simply do not fit onto the overhead shaft. Furthermore, if the radial distance between the overhead shaft and the collar is limited, the spring tail may not be property hooked onto the collar which might in turn render the counterbalancing inoperable and/or unsafe and may also lead to the spring tail damaging the outer surface of the overhead shaft which is also undesirable for reasons well known in the art. The above-described problems are inherent to the collars known in the art which are inadequate for those cases where the space between the inside of the plug and the shaft (which may or may not be covered with an additional fitting) is small.
Another major problem is that none of the types of collars known in the art provide a simple, quick, reliable, and cost effective way for operatively connecting a torsion spring having a reduced inside diameter to an overhead shaft of a counterbalancing mechanism used for garage doors and the like.
Hence, there is a need for a more compact, more reliable, easier to use, easier to maintain, safer, quicker, and more cost effective device for operatively connecting torsion springs to overhead shafts of counterbalancing systems used for cable-operated doors, such as garage doors for example, particularly for when the space between the inside of the plug and the shaft (which may or may not be covered with any additional fitting) is limitedly small.
The object of the present invention is to provide a xe2x80x9cplugxe2x80x9d, also known as a xe2x80x9ccollarxe2x80x9d, an xe2x80x9canchorxe2x80x9d, or a xe2x80x9cconexe2x80x9d, which satisfies some of the above-mentioned needs and is thus an improvement over the devices known in the prior art.
More particularly, the object of the present invention is to provide a new approach for operatively connecting torsion springs to overhead shafts of counterbalancing systems used for garage doors and the like.
In accordance with the present invention, the above object is achieved with a plug for use in a counterbalancing mechanism of a cable-operated door, said plug being used for operatively connecting an overhead shaft to a torsion spring co-axially mounted onto said shaft, said plug comprising:
a cylindrical collar having opposite first and second portions, the first portion being used for receiving a coiled segment of the torsional spring, the collar being provided with a hooking slot positioned between the first portion and the second portion of the collar for hooking a free end of the torsion spring onto said hooking slot; and
a cylindrical flange rigidly affixed to the second portion of the collar, said flange being used for transferring a torque between the torsion spring and the overhead shaft when the flange is securely fixed about the overhead shaft;
wherein the collar of the plug is eccentrically mountable about the overhead shaft so as to allow a portion of the free end of the torsion spring to be lodged between the collar and the overhead shaft.
The objects, advantages and other features of the present invention will become more apparent upon reading of the following non-restrictive description of a preferred embodiment thereof, given for the purpose of exemplification only with reference to the accompanying drawings.